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How long should you leave a mattress to expand for?

When you first get a new mattress that comes vacuum-packed in a box or rolled up tightly in plastic, it can take some time for the mattress to fully expand and reach its proper size and shape. Here’s a look at how long you typically need to let a compressed mattress expand before sleeping on it.

What Causes a Rolled Up Mattress to Expand?

Mattresses that come compressed for shipping contain flexible polyurethane foam that has been squeezed down under high pressure. When you cut open the packaging, the foam inside the mattress begins to slowly expand back to its original shape.

This expansion process relies on exposure to air. As air particles enter the foam’s open cell structure, the foam recovers its loft and dimensions. The time it takes for a compressed mattress to fully expand depends on factors like:

  • The type of foam – Memory foam takes longer to expand than polyurethane foam
  • Mattress thickness – Thicker mattresses take longer to expand
  • Compression level – More tightly compressed mattresses take longer to reach full size
  • Temperature – Warmer environments speed up expansion

How Long Should You Wait Before Sleeping on a New Mattress?

Most manufacturers recommend allowing 24-72 hours for a rolled or vacuum-packed mattress to regain its full shape and height. Here are some general guidelines for expansion times:

Mattress Type Recommended Expansion Time
All-foam mattress 24-48 hours
Hybrid mattress 24-48 hours
Latex mattress 48-72 hours
Innerspring mattress 24 hours

Memory foam and latex mattresses usually need the longest expansion time. The dense structure of these foams makes it harder for air to fully penetrate and fill out the material. All-foam, hybrid, and innerspring mattresses containing polyurethane foam recover more quickly.

Tips for Mattress Expansion

Here are some tips to help a compressed mattress expand correctly:

  • Unbox the mattress in the room where you plan to use it
  • Carefully cut away all plastic with a utility knife or scissors
  • Allow the mattress to expand on a flat, solid surface like the floor or bed frame
  • Don’t place the mattress on a slated bed base until fully expanded
  • Give the mattress plenty of space and don’t put pressure or weight on it while expanding
  • Keep the room temperature warmer to speed up expansion
  • Gently walk and knead across the surface to loosen foam
  • Leave all bedding off until fully expanded

How to Tell if Your Mattress is Fully Expanded

Once sufficient time has passed for your specific mattress type, inspect it to see if it has reached its maximum size:

  • There should be no creases, folds or compression lines
  • The surface should be flat and even, not wavy or indented
  • Measure the height and check it matches the specs from the manufacturer
  • Gently press down to feel if the foam has softened and become springy
  • The mattress edge should form a smooth, squared-off corner
  • You should no longer detect any lingering off-gassing odors

If you notice dips, bumps or unevenness, allow more time for expansion. Kneading these spots gently can open closed cells. If some areas still seem compressed after 72 hours, contact the manufacturer – this may indicate a defective product.

Is it Okay to Sleep on a Mattress Before Full Expansion?

It’s best to wait until your new mattress reaches its maximum height before using it. Sleeping on the mattress too soon can:

  • Prevent the foam from expanding fully
  • Create permanent indentations and sagging
  • Compromise back support and comfort
  • Void the warranty if damage occurs

Minor impressions where you lay may recover over the first few weeks as the foam continues to settle. But major sagging or misshapen spots can’t be reversed once the foam cells break down. Letting the mattress expand properly extends its lifespan.

Other Mattress Expansion FAQs

Why Won’t My Mattress Expand Fully?

If a compressed mattress won’t reach its proper dimensions after 3-4 days, there may be an underlying issue. Reasons your mattress gets stuck part-way expanded include:

  • Being blocked by furniture or bedding materials
  • Not enough exposure to air circulation and ambient heat
  • The foam has damage or defects
  • Mattress layers weren’t sewn together properly
  • Too much early use compressed the foam

Check for any obstructions preventing expansion. Try kneading and flexing problem areas to open closed cells. If size issues persist, report them to the retailer or manufacturer.

Can You Speed Up Mattress Expansion?

There are a few tricks to help a compressed mattress spring back faster:

  • Move it to a warm room around 70-75°F
  • Regularly massage, walk on, and flex the mattress
  • Use a fan to blow air over the surface
  • Elevate foam near edges that expand slower
  • Don’t repackage or recompress during transit

However, never try to accelerate expansion by applying direct heat sources. Exposing memory foam to excess heat can damage or misshape it.

Should You Rotate a New Mattress While Expanding?

Most manufacturers recommend against flipping or rotating a mattress during the initial expansion period. Letting it settle undisturbed helps the foam regain its strength and form. Once fully expanded, you can then rotate the mattress as directed.


Allowing enough time for your compressed foam mattress to reach maximum size is crucial for performance and durability. Follow your mattress maker’s advice for the ideal expansion time frame. While it requires some patience initially, taking these steps ensures your mattress lasts for years of comfortable sleep.